Ultrasound-enhanced Zero-valent Copper Activation Of Persulfate For The Degradation Of Bisphenol AF

As an alternative to the endocrine-disrupting hormone bisphenol A?BPA?,bisphenol AF?BPAF?was confirmed to have endocrine interference effect likewise.Advanced oxidation processes are a new water treatment technology in recent years,mainly by generating active free radicals,such as the hydroxyl radical?·OH?and sulfate radical(SO₄^?-),to degrade organic pollutants in water.Of note,advanced oxidation processes based on SO₄^?-are more suitable for practical application because they are wildly applicable and have both stronger and selective oxidation performance.Persulfate?PS?can produce massive SO₄^?-after activation.In recent years,researchers concentrated on various new type of PS activation methods,but most of them only focused on the degradation efficiency.Therefore,further study of PS activation mechanism and exploring the transformation rule of free radicals in the system are conductive to applying the advanced oxidation process based on SO₄^?-to actual water repair.Firstly,ultrasound?US?was introduced into PS/zero-valent copper?ZVC?to strengthen the activation process.The degradation of BPAF effectiveness in PS/ZVC/US system was studied by compared with PS/ZVC,PS/US,ZVC/US,PS,ZVC and US system.And the BPAF degradation in the PS/ZVC/US process was fitted into pseudo-first-order kinetics,obtaining BPAF degradation kinetic parameters for the subsequent analysis.Finally,according to the kinetic analysis of the influence of pH on the degradation of BPAF and the establishment of the free radical contribution mathematical model,the free radicals that played a major role during the degradation of BPAF in PS/ZVC/US system under different pH conditions and after different reaction time were quantitatively studied to explain the reason for segmentation of the pseudo-first-order fitting curve of BPAF degradation in PS/ZVC/US system.Secondly,with analysis of the role of US and ZVC in PS/ZVC/US system,the mechanism of the synergy between US and PS/ZVC system was studied and found that heterogeneous reaction process was the key step to produce free radicals,involving the generation of strong activator?Cu⁺and the activation of PS absorbed on ZVC surface by?Cu⁺.The homogeneous reaction produced a certain of active free radicals and Cu³⁺which could also degrade organic matter.But due to the low concentration of Cu⁺and the unstability of Cu³⁺,the homogeneous process played a limited role in BPAF degradation.In addition,the influencing factors for the degradation of BPAF were also studied,including initial concentration of oxidant and BPAF,and coexisting anions(nitrate ions?NO₃^-?,sulfate ions(SO₄^2-),chloride ions?Cl^-?and bicarbonate ions?HCO₃^-?).Finally,the degradation intermediates and pathways of BPAF in PS/ZVC/US system was studied.BPAF was firstly taken an electron by oxidant,and three conjugates were generated under the influence of electron delocalization effect.The subsequent degradation was divided into two pathways.The first one was that one of the conjugates transformed to a hydroxylation product under the attack of·OH,and then mineralized and degraded into small molecules such as CO₂ and H₂O.As for the Second pathway,conjugates went through?-scissor generating benzoquinone and cationic free radicals under the attack of oxidants such as·OH and SO₄^?-.Finally,all the intermediates would be complete mineralized.